The intestinal immune organ is generically referred to as gut-associated lymphatic tissue (GALT), and mainly constituted of Peyer's patch, mesenteric lymph node and intestinal epithelium. Foreign substances (antigen) such as pathogens and the like that invaded the intestine are incorporated into M cells of Peyer's patch, and presented to T cells by antigen presenting cells such as dendritic cell and the like present in Peyer's patch. Simultaneously, B cells also recognize the antigen, and class switching from IgM+ B cells to IgA+ B cells occurs by cytokine stimulation to finally become plasma cells that secrete immunoglobulin A (hereinafter to be referred to as “IgA”).
The number of intestine-specific IgA producing cells is about 70-80% of the plasma cells present in the whole body, and IgA secreted from the plasma cells afford infection defense such as inhibition of attachment of pathogens to the mucosal epithelial cells, neutralization of toxins and enzymes produced from pathogens by IgA binding thereto and the like. Therefore, it is highly important to activate intestinal immunity by IgA production to maintain balance of the immunity.
In recent years, the number of patients having allergic diseases is rapidly increasing. Such patients tend to show a decrease in the intestinal mucosal immunity, and therefore, the enhancement (development) of intestinal mucosal immunity is considered to highly possibility lead to the prophylaxis thereof.
As bacteria having an IgA production promoting ability and capable of enhancing intestinal immunity, Lactobacillus plantarum AYA strain (patent document 1), Lactobacillus gasseri strain (patent document 2) and the like have been reported.
Lactic acid bacteria are isolated from various plants such as raw vegetable, pickles and the like and added to foods, drinks and the like as a probiotic. However, since reports of lactobacillus having an IgA production promoting ability and capable of activating the intestinal immunity are limited to the above-mentioned documents and the like, provision of new lactic acid bacteria having a high IgA production promoting ability has been desired.